1. Field of the Invention
The present invention relates to a heat assisted magnetic recording head that is included in a magnetic recording apparatus and heats a recording region in a magnetic recording medium during magnetic recording, and also relates to a heat assisted magnetic recording apparatus using the same.
2. Description of the Related Art
Information is recorded onto a magnetic recording medium such as HDD (Hard Disk Drive) and DASD (Direct Access Storage Device) by using a recording element of a magnetic head that moves above the magnetic recording medium while floating. Moreover, digital information recorded on the magnetic recording medium is detected by using a reproduction element of the magnetic head. It is necessary to increase coercivity Hc of a recording layer and make a grain diameter (D) of crystals of a material forming the recording layer smaller in order to increase a recording density of the magnetic recording medium. However, when the crystal grain diameter is made smaller, thermal disturbance may make magnetization of crystal grains in which information is recorded unstable or disappearance of recorded magnetization, for example.
It is desirable that a value of Ku·V/k·T is 70 or more in accordance with a guideline for showing a state of stability of magnetization, where Ku is an anisotropic energy, V is a volume of a crystal grain, k is Boltzmann constant, and T is an absolute temperature.
Thus, development of a recording film having an anisotropic energy that is on the order of 107 erg/cc, such as FeCo and CoPt, has been advanced in order to achieve high-density recording in which a recording density is several hundreds of gigabits per square inch.
However, Ku and Hc have a relationship that Hc nearly equals to 2 Ku/Ms under primary approximation, where Ms is saturated magnetization of a crystal grain. Thus, when Ku is made larger, Hc also becomes larger and may exceed 10 kOe that is twice or more Hc (3 to 4 kOe) of an actual magnetic recording medium.
Recording of information onto a magnetic recording medium is achieved by a recording magnetic field generated by a recording element of a magnetic head, as described above, and it is believed that the recording usually requires application of the recording magnetic field that is about twice as large as the aforementioned coercivity Hc. The intensity of the recording magnetic field is determined by the shape of a recording element, the saturated magnetic flux density Bs of a material for the recording element, and the like. Especially, the saturated magnetic flux density Bs largely affects the intensity of the recording magnetic field.
At the present day, a recording element material having Bs nearly equal to 2 T (tesla) is at a leading edge of practically usable recording element materials. Moreover, it is shown in a Slater-Pauling curve that 2.4 T is a limit of a practical level of Bs. Therefore, it is very difficult to record digital information onto a recording film having Hc larger than 10 kOe.
In order to overcome the above problem, a method called as heat assisted recording has been proposed, in which a light beam that can form a converged spot is made incident on a magnetic recording medium so as to heat a recording film while a recording magnetic field is applied to the magnetic recording medium by means of a magnetic head. In this manner, while Hc of the recording film is lowered, information is recorded onto the recording film. Japanese Patent No. 3471285 proposes a magnetic head with a heat source and/or a heat sink mounted thereon in conjunction with the principle of the above heat assisted recording. Japanese Patent No. 3441417 proposes a magnetic head including an opening for near-field emission. Japanese Patent No. 2665022 proposes a method in which an arc-like recording pattern is formed.
However, Japanese Patent Nos. 3471285 and 3441417 do not disclose how to mount various members for achieving assist with a heat, such as a heat source, an optical path, and a heat sink on a small magnetic head having a slider length of 1 mm or less that is actually needed in a compact manner. Moreover, in an actual use, a power of a light beam is not sufficient for heating the recording film to a high temperature and it is necessary to separate a magnetic system and an optical system from each other as measures for a heat. However, Japanese Patent Nos. 3471285 and 3441417 do not disclose how to overcome those problems.
Furthermore, the technique of Japanese Patent No. 2665022 has a problem that the arc-like recording pattern is largely affected by an edge noise and crosstalk.